Polar CS100 average speed does not seem accurate

Ally83 Posts: 3
edited April 2012 in Road beginners

I bought a polar cs100 computer and have been using it for a month now my average speed says 15mph or there abouts. I also use imapmyride on my iphone so that I can record the route on a map and noticed my average speed is about 23mph. So i decided to work it out for myself based on the miles I cycled and the time it took. The app seems more accurate. Has anyone else had this problem as both the computer and app are recording a similar distance and time but the computer seem to by way out with the average speed.

(last ride was 34.7miles and took 2 hours 20 minutes. Which I calculate to be an average speed off 24.78mph)

Maybe my calculations are incorrect


  • jameses
    jameses Posts: 653
    Ally83 wrote:
    (last ride was 34.7miles and took 2 hours 20 minutes. Which I calculate to be an average speed off 24.78mph)

    Maybe my calculations are incorrect

    I make that about 15mph.
  • jim453
    jim453 Posts: 1,360
    Speed is distance divided by time taken. You may need to be careful how you express the time in the calculation because 2 hours 30 mins is 2.5 hours not 2.3 hours for instance.

    Just trying to understand how you could have messed up the calculation.
  • wheezee
    wheezee Posts: 461
    I get 17.56mph.
  • dabber
    dabber Posts: 1,937
    It's 14.87 mph as posted previously.

    The manual calculation is....
    34.7 miles divided by the number of minutes taken, in this case 140 minutes.
    This gives you a distance of 0.24785714285714285714285714285714 miles travelled for each minute of the ride.
    To give an average miles per hour you multiply by 60.

    60 times 0.24785714285714285714285714285714 = 14.87
    “You may think that; I couldn’t possibly comment!”

    Wilier Cento Uno SR/Wilier Mortirolo/Specialized Roubaix Comp/Kona Hei Hei/Calibre Bossnut
  • rpd_steve
    rpd_steve Posts: 361
    This is just silly. :P 2 hours 20 mins is 2.333 hours.

    s=14.87 miles per hour :idea:

    The comp is right, the app is wrong. Often GPS can be patchy of phones. The Polar should alow you to see your GPS accuracy - typicly about 24 ft on my Garmin 800, so it knows where I am +- 8m. So on an 8m ride it may get my speed out by 100% but on a 50 km ride it is accurate to 0.016% of exact.

    And with the greatest respect a 24mph average would have been very impressive over 35 miles, particulally if you are solo, which I assume you are as otherwise you would have asked a fellow ride their average. If you was capable of 24 mph you would dam well know it! 8)
  • Ally83
    Ally83 Posts: 3
    Thanks guy realised I was converting the time into minutes and the app is giving the wrong units.

    Feel like an idiot now lol
  • t5nel
    t5nel Posts: 365
    Was the app reading in km/h?

    15mph ~ 24km/h
    My bikes
    MTB - 1997 Kona Kula
    Hybrid - Kona Dew Deluxe
    Road - 2011 Ribble Gran Fondo, Omega Matrix Ultegra
  • team47b
    team47b Posts: 6,425
    Now, if you had a bike computer that said you were averaging 24mph when doing 15mph you could make a few bob selling that on this forum.

    Yeah I realise there are a few people with these already :D

    This is intended to be humuorous and any similarity with real people is purely co-incidental keep your toys in the pram
    my isetta is a 300cc bike